The present invention relates to a method and an apparatus for supplying vacuum to a traveling-type servicing device which is designed to perform a servicing operation such as yarn piecing or automatic package doffing at the individual stations of a parent multi-station textile machine such as a spinning frame, winder or fly frame.
In a servicing device, such as a yarn piecing or package doffing device, which serves the parent textile machine having an array of stations while traveling therealong, it is commonly known that vacuum has been extensively utilized by such a servicing device for the purpose of grasping a free end of a broken yarn or drawing in residual pieces of yarn for removal thereof. Though the servicing device is equipped with a tube or a nozzle for taking in vacuum, no vacuum source such as a blower is usually provided in the servicing device for the sake of reduction of weight and size thereof. Instead, a duct connected to any suitable source of vacuum and having vacuum outlet openings which may be covered by lids is arranged extending along the machine, and the servicing device positioned at any of the stations to be served thereby receives necessary vacuum from such a duct.
As a known method, e.g. U.S. Pat. No. 3,077,311, in which the servicing device takes vacuum from a duct, the duct has vacuum outlet openings formed on its face so as to correspond to the individual stations of the parent machine, and a cover plate or a lid is swingably supported on the duct for each of the vacuum outlet openings in such a way that the swinging motion of the lid can open and close the outlet opening. On the other hand, the servicing device has a vacuum supply tube projecting therefrom toward the duct and having an end which is normally placed in a sliding contact with the duct while the servicing device is in motion and engageable with the lid so as to swing it and, thereby, to open the vacuum outlet openings. This method is disadvantageous, however, in that the end of the vacuum supply tube wears rapidly because it is subjected to constant friction due to sliding contact thereof with the duct while the servicing device is traveling along the parent machine. Furthermore, each time the servicing device moves past the stations, the lid is caused to swing thereby to open even the vacuum outlet openings for those stations which need no yarn piecing or package doffing service by the servicing device. Therefore, ambient air is allowed into the duct through the opened vacuum outlets, with the natural result that sufficient degree of airtightness between the lid and the vacuum outlet opening cannot be maintained. In addition, the lid returns by its own weight to its original position where the vacuum outlet opening is covered with the lid, there is a fear of further decrease of airtightness due to poor reliability in lid motion.
An attempt to improve the above-mentioned method was made by the Japanese Patent Publication 49-1668, according to which the vacuum supply tube is arranged so as to be movable toward and away from the vacuum duct, and the lid which is formed into a multiple-petal shape is rotated by a pin which is moved by and with the servicing device along the parent machine, whereby the vacuum supply tube is connected to the vacuum outlet opening by moving forward to the duct only when any station is to be served by the servicing device. In this method, however, the multiple-petal lid is rotated by the pin each time the pin moves therepast. As a result, poor airtightness remains unsolved and frequent rotating action of the lid promotes wear between the lid and the duct surface.